Pavement and process for making the same



G. A. HENDERSON AND H. K. STEPHENSON. PAVEMENT AND PROCESS FOR MAKINGTHE SAME.

APPLICATION FILED APR. 15,1920. KENEWED JAN. 4. 1922.

Patented Mar. 7 1922.

2 SHEETSSHEET 1- G. A. HENDERSON AND HE K. STEPHENSON. PAVEMENT ANDPROCESS FOR MAKING THE SAME- APPLICATION FILED APR. 15,1920. RENEWEDJAN. 4, 1922.

1,409, 1 ()4, Patented Mar. 7, 1922.

2 SHEETS-SHEET 2- "AN l ,supplied by the UNITED STATES PATENT OFFICE.

GEORGE A. HENDERSON AND HENSON K. STEPHENSON,

OF ST. ALBANS, WEST VIR- PORATION OF DELAWARE.

PAVEMENT AND PROCESS FOR MAKING THE SAME.

Specification of Letters Patent.

Application filed. April 15, 1920, Serial No. 874,078- Renewed Ianuary4, 1922. Serial No. 527,056.

To all whom it may concern:

Be it known that we, GEORGE A. HENDER- SON and HENSON K. STEPHENSON,both citizens of the United States, residing at St. Albans, in thecounty of Kanawha and State of West Virginia, (whose post-office addressis St. Albans, West Virgin1a,) have invented new and useful Improvementsin Pavements and Processes for Making the Same, of which the followin isa specification.

The invention re ates to improvements in compositions for paving andlike structures in which pitch is used as the impregnating and cementingagency of vegetable and mineral matter, and the object of the inventionis to produce inherent stability. and density of such roducts as aredescribed in the said Hen ersons United States Patent No. 1,040,321 ofOct. 8, 1912 and his co-pending application for Letters latent, SerialNumber 212,194 of 1918, for pavements and process for making the same.

The invention will be best understood by reference to theaccompanyingdrawings, it being premised that various changes may be made in theapparatus within the scope .of the appended claims. Fig. 1 is a sideelevation artly in section, Fig. 2 a cross section and Fig. 3 an endview of apparatus adaptable to the process. F ig. 4 is a detail,sectional view of a compression die; in which drawings A represents theframe work upporting the machine, C a furnace, D an asphalt heating tankheated by the furnace, within the lines of which tank are rigidly hungan impregnating drum (I), H a screw conveyor and its housing, G anaggregate chamber, F a dust ho per, F a gate valve to'chute F to drum inwhich all of the ingredients are a 'tated under indirect. heat eatedbitumen in tank D partially surrounding the drum 1, and by direct heatsucked from the furnace C therethrough by exhaustergK and thendischarged in a continuous flow of material under pressure throu hdrum-mouth L into vacuum chamber all for the purposes hereinafterdescribed.

In carrying out the invention fibrous particles, preferably that spenthard wood .de-

scribed in said Patent 1,040,321, but while containing water in lieu ofsap and cellular tissue removed therefrom, are subjected to the actionof bicarbonate of soda in solution to neutralize any remainingpyroligneous acids of such woody particles. These woody particles arethen only partially dried while being heated and agitated under theinfluence of suction in said drum I until their moisture content isreduced to approximately 20% of their solid volume. In this operationthe wood dust, when sufliciently dry to float in air suspension, issucked out of the drum Patented Mar. 7 1922.

by exhauster K before such dust becomes hydro-carbon, and the clean,partially dried woody particles are then taken from the vat, bagged, andweighed in predetermined quantity for use in the process as hereinafterdescribed.

It has been heretofore proposed to mix in excess of fifty per cent. byweight of truly impalpable dust of earthy nature with a bituminouscompound of relatively soft consistency,'as tested for penetration,viz., approximately 100-120 penetration, which bi tuminous compound ismore of a lubricant permeating such dust than it is a binder such as theheavier bituminous compound of approximately 4050 penetration used inthe so-called mixing-method of producing paving structures, asdistinguished from the penetration method both known to the trade andprior art. In order to practically agglomerate in colloidal suspensionsuch substantial pro ortion of impalpablemineral dust in suc a heavybituminous binder,

to act as a filler of voids between, (as distinguished from poreswithin) particles of larger aggregate sought to be bound thereby, wepreliminarily prepare a mixture of such dust of colloidal nature, and offrom 5% to 20% pulverized sulfur, of 1%-to 4% sodium chloride, and from1} of 1%t0 3% 'of sulfate of copper, in proportions'in rela tion to thefinal product constituents hereinafter described, and in'ect thismixture in air suspension, under t e influence of heat and suction, intoa mixture of larger mineral and vegetable aggregate, while agitating thesame in a drum, (1), durin dehydration of that mas in the presence 0molten bitumen.

We have discovered that by this means we obtain temporary fluidity ofthe bituminous cement and substantial ebullition of the mass, the steamthere and then evolved acting as the carrying agent to perfectlyagglomerate the bituminous cement uniformly throughout the aggregate andto aid in colloida 1y suspending the dust therein, andfacilitatingchemical combination and vulcanization of the ingredients. 1

Depending on the nature of the product of our process, as regards'itsconsistency, degree of hardness and of elasticity, the proportions ofdust and chemicals are varied. In/example, to provide a mastic filler asa matrix within interstices of larger metal of a macadam highway, weprefer the following proportions: the final product shall containbitumen containing by weight the derivative of one per cent. sodiumchloride, copper sulfate one per cent, sulfur five per cent. and 93%pitch cement or bitumen, known to the trade, and the product of thisprocess shall contain, in example, of sulpho-chlorinated bitumen, 30%impalpable mineral dust, 20% woody particles freed from vegetable dustas in the above manner described, and 20%-larger mineral aggregatecomposed of crushed stone, slag or gravel, containing all dust offracture, representing in approximate volume the following proportions:viz., of bituminous compound 36%, impalpable dust 20%, vegetableparticles, in the absence of dust, 32%, mineral aggregate 12%. In ouruse of kieselguhr or other light weight impalpable mineral dust, thevolume percentages shall be identical with the above, with correspondingchanges in proportions by weight.

In operation of said apparatus the vegetable particles, in the absenceof dust, are deposited in predetermined measured proportion in mixer Esimultaneously with the depositing therein of the predetermined measuredquantity of pitch heated to fluidity in tank D, by heat in furnace Csupplied by burners C with oil under air pressure throughsupply pipe Cfrom a fuel oil tank carried on traction unit forward of the plant, notshown in the drawings.

Tank D is initially charged from an auxiliary supply, with heatedbitumen, through inlet pipe D. By operating threeway cock D the heatedbitumen is sucked through pump X, cock D and pipe D to tank D. Whencharged with hot bitumen the supply to tank D is shut off by closing theinlet through cock D in pipe D, which operation opens suction throughpipe D and the pump then operates to suck the heated bitumen up from thebottom of the tank D on one side of drum I and to deposit it at the topof tank D on the reverse side of drum I, which action is designed to (a)furnish a ready supply of heated bitumen through cock D manuallyoperated to 'charge pitch weigh-bucket, not-shown, for

depositing the measured quantity of pitch 'into mixer E, and (b) tocause continuous agitation of the heating bitumen .in tank D, to preventcokingof the mass therein.

The pitch in excessive quantity in relafinal product if such excess werenot taken up by the added dust in the manner hereinafter described, bythe action of interdigitating blades E, E anchored to reciprocatingshafts E E revolved in the same] direction as each other by cog E ondriven shaft E (Fig. 3) operating cogs E, E bearing the blades E E(Fig. 1) aforesaid, connected through driven shaft E with the motivepower P in the manner shown.

When the three ingredients just mentioned have been mixed in mixer E oneminute, and after each particle of the mineral and the vegetableaggregate has been coated with the pitch, the mass is dumped, by manualoperation of lever L (Fig. 1) designed to open the bottom of pug mixerL, in halves, E", E (Fig. 2) (as per known construction,) into aggregatechamber G subjected to suction through pipe G to exhauster K, whereuponthe operation in mixer E is repeated.

Simultaneously with the above mixing operation, the aforesaid dust mixedwith chemicals, is, in predetermined measured quantity, deposited inhopper F, from which it is gradually fed to chute F through gatevalve Foperated by cogged connection F meshing with cog F on driven shaft L andthe dustis precipitated by gravity through chute, F in continuous flowto the entrance to drum I at the point shown in Fig, 1 as I At thispoint the hot air and fumes from the furnace C are sucked into the drumI, carrying said dust thereinto in air suspension by the operation ofexhauster K. The number of revolutions per minute of gate-valve F isfixed consistent with the capacity of the entire machine and itsconnections with driven central shaft I (Fig. 1) and motive power P.

It is designed that the excess pitch in preliminary mixer E shall bepartially taken up by the mineral aggregate therein added, and finallysuch excess exhausted by the addition of the dust in drum I in themanner above described,.so that in the final product the properpercentages of each of the ingredients may be present.

The housing of screw conveyor H forms the bottom of chamber G and thatconveyor is designed to be revolved at a speed consistent with theobject to move the contents of chamber G, viz., one batch of ingredientsfrom mixer E- from chamber G the length of conveyor E within fiveminutes time, the mixing operation in mixer E being repeatedly completedevery five minutes including the time in which the ingredients aremixing therein, and that time required for dumping mixer E to chamber G,thus providing a continuous flow of mixed and measured ingredients todrum I, for the purpose of providing a continuous flow of material outof drum I into vacuum discharge cham ber M.

The period of agitation within drum I is fixed by the speed of thecentral shaft I, and

. its blades I, driven by chain I and pulley I connected with the motivepower P, and by the number, inclination and dimensions of agitatingblades I anchored to the central shaft by sleeves I", which blades areset at such an angle to the centralshaft to form a perfect screw intheir operation to move the mass in drum I the entire length of the drumwithin five minutes. During this period the mass is subjected toagitation, and to such suction by exhauster K as to produce a partialvacuum within drum I,'equivalent to approximately two thirdsatmospheric, viz. 466 barometric pressure, at'which pressure the boilingpoint of water (that residual moisture within the aggregate then beingde hydrated) requires a temperature of not exceeding 88 C (190 deg.Fahr.) as compared with 100 deg. C., (212 deg. Fahr.) at atmosphericpressure. In this connection we have discovered that such reducedpressure within the mass inclosure I aids in it's ebullition, as and forthe purpose herein;

after described, namely:

The exact temperature of the mass within drum I is essential to beuniformly fixed and registered for the purposes of this process, andthis wev accomplish by regulating the degree of heat of the bitumen intank D, by manually fixing the degree of pressure and quantity of oilsupply to the burners G which burners indirectly heat, through thebitumen in tank D, the contents of mixer E, conveyor H, and drum I inthe manner shown in Fig. 1. The heat in drumI is further regulated bymanually adjusting sliding valve I ('Fig. '1.) through which valve ,airof atmospheiic temperature is admitted and mixed with that hot air fromthe furnace C. The temperature of the mass in drum I, thus fixed, isregistered by a hand thermometer as it emergesfrom drum I, and by theuse of fixed thermometers set within the lines of drum I and tank Drespectively, at the points shown in Fig. 1 at T T When in drum. Iextreme fluidity of the mass (producing a honey-combed effect) is causedby steam in evolution from said residual moisture, escaping from thepores of the woody particles, abnormally enlarging the pores thereof,and entrapping the bituminous cement therein, under the infiu-. ences ofsaid suction and heat, agitation of the mass, and instantaneous actionof the chemicals introduced thereto in air suspension with the dust,which action perfectly disseminates the bitumen throughout the mass and.entraps the dust therein while the bitumen is in a state of momentaryebullition sufficient in time and extent for the designed purpose, viz.,the colloidal suspension of dust in the bitumen. When the mass iscompletely dehydrated in this manner, the chemicals are married in acombined state. with the bitumen, at which time the ebullition at oncesubsides.

The mass in drum I in completing its passage therethrough is subjectedto slight compression by the action of blades I ,which compact the samethroughdrum mouth L. This compacting aids in the removal of residual gasand air bubbles from the hot mass, by its suction to the atmospherethrough exhauster K..

. In the above operation the impalpable particles of dust are separatedfrom their neighboring particles of dust by the thinnest possible filmof the heavy bituminous compound (as distinguished from that bituminousbinder composed of sulfur and bitumen such as described in HendersonsUnited States Patents Numbers 1,264,932 and 1,266,261 of 1918.) Thecombination of the said chemicals with the bitumen, and the entrappingtherein in colloidal suspension of said substantial quantity of impalpable mineral matter, is due, in our opinforming a honey-combingeffect) which, nevertheless, sets to density and afterwards hardens inthe final product to the extent of the predetermined quantity of saiddust and chemicals, within the said limits, present inthe o eration. '1

Chamber (Fig. 1) is continuously closed at its mouth and discharge endby the material pressed through them. The action of exhauster K,connected therewith by exhaust stack M produces within chamber M partialvacuum to-wit: that equivalent to'a barometric pressure of 152 mm. orapproximately one-fifth normal atmospheric pressure. This condition, inconjunction with the means for compacting the material in chamber M, isdesigned to free it from any residual gas or air preliminary to finalcompaction of the mass in the manner hereinafter described. In chamber Mthe shaft of screw conveyor M driven b the machines motive power byconnection as shown, is operated horizontally whereas the bottom ofchamber M is'constructed so as to provide an upward grade ofapproximately ten er cent. toward the compression die Y. he

conveyor M converges in its pitch in ratio fio .Strated in practice,sufiicient resistance to the onward movement of the plastic material inthe chamber M toward and through\ die Y to effect substantialcompression of the material in chamber M before it reaches the die, toentirely free it of its residual air and gas content within the vacuuminfluence 1 in chamber M provided. In this manner we and meshing withcogged drums C, bearingaxles C C operate independently of each avoid theentrapping of air and gas in the mass when finally compacted in mouldsor otherwise, and inherent stability and density of our product isincreased over that of the prior art in this manner.

The degree of compression to be applied to our product of this processis fixed by the dimensions of the die Y in relation to the power appliedto compact the material through it. After emerging from the die in acontinuous flow the hot, plastic material is compacted in mbulds toshape, or when used as a matrix to fill the voids between the largerstone'of macadam highway, in example, as described in the applicantHendersons co-pending application Serial Number 212,194,"of 1918, thematerial consisting of said denatured hardwood chips, impregnated withbitumen in the absence of wood dust, mixed with larger mineralaggregrate precoated with bitumen, and filled with bitumen, colloidallysuspending mineral dust chemically treated in the manner hereinabovedescribed, is spread over and compacted within the interstices of largermineral aggregate, in situ, on a highwa in the followin manner,illustrated in ig.1:

Mu tipedal units 0 0 passing around other to support the machine byconnection with its frame work A, in its course forward; and constitutethe sides of furnace-C.

to prevent lateral suction of outside air to the furnace C. The ends offurnace G are composed of heavy leather strips C, C, inserted in steelmembers to scrape over the roads surface, for' like purpose. ScarifiersB suitably attached to the frame work of the machine, by resilientmembers, not shown, (but known to the trade) are designed to ,plow theroad for a depth of from-two to three inches, and to loosen the stoneaggregate thereof. Suction through furnace 0,- caused by the operationof exhauster K, is designed to suck up from the interstices and surfaceof the road, such dust as may be loosened from its aggregate by thescarifiers in combination with the blasts of flame and air, "underpressure, from burners C, C, directed onto said road; and to depositsaid dust, in air suspension, into drum I in a continuous operationduring the above de-' scribed process in which additional dust,containing the aforesaid chemicals, is likewise earned in air suspensionwithin drum I. We have discovered in practice that,

within relatively close limits, the quantity of v dust removable fromthe road itself, is sufficient to produce the desired density of ourproduct when added to that dust injected to the mass through chute F Inpractice we specify and incorporate in the mass considerably more dustthan is required to fill all voids between the larger particles whensuch dust is colloidally suspended in the bituminous compound; and havediscovered that when such an excess of this mixture is present thestability and density of the product i is correspondingly increased.

The dust-cleared, loose stone of the highway, heated by saidflame-blasts in the course of the machine over it, is then coated withpreheated bitumen from an auxiliary supply within a traction unit (notshown), throu h bitumen supply ipe O' and said heated bitumen is forcedt rough pipe 0 by air compression, to rotary penetration nozzles O atthe rear of the machine, into. the interstices of the scarified surface;As the machine passes over this surface the matrix of the' processhereinabove described, is chuted to place thereover in quantityapproximately one inch in thickness, manually raked to shape andcompacted into the open, dustcleared, bituminized interstices of theheated stone in situ.

We claim:

1. The herein described process which consists in mixing moist vegetableparticles in the absence of vegetable dust with an excess of bitumenpreheated to a temperature above, the boiling point of the moisture;then mixing therewith mineral aggregate in relatively large sizes; thenagitating the mass in a vat subjected to suction under the influence ofsuiiicient applied heat to completely dehydrate the same while graduallyintroducing in air suspension and entrapping thereinimpalpable mineraldust pre- 'mixed with sulfur, sodium chloride and copper sulfate, inquantity suflicient to adsorb the excess bitumen; then subjecting themass to heat and pressure in partial vacuo and compacting the same toshape.

2. The herein described rocess of treating a metal highway conslsting invmixing and dehydrating mineral and vegetable ag-, 1

gregate in the presence of an excess of pure bituminous binder in a vatunder the influence of sustained heat and sucti n sufficient for thepurpose, while adding thereto in air suspension impalpable dust suckedtherein from interstitial spaces of the highway created by scarifyingthe same, and

blowing flame and air there into, simulta-' neously depositing in airsuspension within said vat additional dust mixed with sodium chloride,copper sulfate and sulfur suflicient in quantity to adsorb the excessbituminous binder, heating said scarified metal of the highway andcausing a bituminous compound to penetrate the same in its dustlessloose, heated condition; then spreading said mixed material thereoverand compacting the same to shape 3. A bituminous composition comprisingmineral and vegetable matter impregnated and coated in the absence ofdust with a bituminous binder, the interstices'between which matterrepresenting at least forty per cent, by volume of the final product,being completely filled with a matrix of mineral dust colloidallysuspended in sulfochlorinated bitumen.

4. A paving structure consisting of a broken stone bas of relative largesizes of stone coated with a pure bituminous binder the intersticesbetween which are filled with mineral and vegetable matter of smallersizes nnpregnated and coated in the absence of dust with bitumen theinterstices between our hands in the presence of two witnesses this thday of March, 1920.

GEORGE A. HENDERSON. HENSON K. STEPHENSON.

In the presence of- L. J. WHITE,

C. H. ZERKEE.

